Dramatic declines in the abundance of anadromous Pacific salmonids have occurred over the last century in the Columbia River basin. Population declines followed harvest, hydrosystem and watershed development, habitat loss and degradation, and reduced survival in freshwater, estuary, and marine environments. These declines are accompanied by greatly reduced levels of natural production due to an array of anthropogenic factors.
Four nursery lakes in the Yakima River Basin, which historically produced an estimated annual return of at least 200,000 sockeye, were removed from production in the early 1900s when irrigation storage dams were constructed without passage. The Yakama Nation is working with the U.S.